Analysis by: Karen Ivy Titiwa
ALIASES:

Ransom:MSIL/Filecoder.DI!MTB(MICROSOFT); HEUR:Trojan-Ransom.MSIL.Encoder.gen(KASPERSKY)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It encrypts files with specific file extensions. It encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 18,944 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 03 Dec 2020
Payload: Displays message/message boxes, Deletes files, Encrypts files

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Ransomware drops the following files:

  • %User Profile%\Delshades.bat → deletes shadow copies
  • %User Profile%\WindowsUpdateTemp.bat → deletes the original executable file

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • %User Profile%\Delshades.bat
  • %User Profile%\Links\!#!READ-ME!#!.txt
  • %User Profile%\WindowsUpdateTemp.bat

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other Details

This Ransomware deletes the following files to remove its traces in the system:

  • %User Profile%\Delshades.bat

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Ransomware Routine

This Ransomware encrypts files with the following extensions:

  • .txt
  • .doc
  • .docm
  • .docx
  • .ppt
  • .pptx
  • .xls
  • .xlsx
  • .txt
  • .pdf
  • .rtf
  • .hwp
  • .wmv
  • .mp4
  • .avi
  • .flv
  • .ogg
  • .3gp
  • .3g2
  • .mp3
  • .wav
  • .wma
  • .flac
  • .m4a
  • .aac
  • .mid
  • .midi
  • .py
  • .js
  • .html
  • .htm
  • .xhtml
  • .php
  • .bat
  • .cmd
  • .vbs
  • .java
  • .jar
  • .json
  • .dat
  • .lock
  • .dat_old
  • .mca
  • .log
  • .gz
  • .xml
  • .sql
  • .odt
  • .sln
  • .cs
  • .vb
  • .vbproj
  • .csproj
  • .manifest
  • .config
  • .resx
  • .resources
  • .pdb
  • .cache
  • .part
  • .xcf
  • .aep
  • .prproj
  • .psd
  • .jpg
  • .jpeg
  • .png
  • .bmp
  • .7z
  • .7zip
  • .rar
  • .zip
  • .tax2015
  • .tax2016
  • .tax2017
  • .tax2018
  • .tax2019
  • .tax
  • .package
  • .cab
  • .jfif
  • .tar
  • .mpeg
  • .mpg
  • .gzip
  • .7-zip
  • .z
  • .db
  • .torrent
  • .arj
  • .ace
  • .apk
  • .cpp
  • .c
  • .csv
  • .syncdb
  • .key
  • .flp
  • .sfx
  • .ibank
  • .contact
  • .usa
  • .car
  • .oga
  • .001
  • .mcgame
  • .disk
  • .unity3d
  • .glob
  • .save
  • .ver0
  • .ver1
  • .ver2
  • .com
  • .cfg
  • .bak
  • .tlb
  • .ttf
  • .ja
  • .owl
  • .xpi
  • .nvram
  • .vmdk
  • .vmsd
  • .vmx
  • .vmxf
  • .vmsn
  • .vmem
  • .appicon
  • .appinfo
  • .menudata
  • .lck
  • .user
  • .rsrc
  • .zipx
  • .myapp
  • .hta
  • .mkv
  • .gif
  • .asm
  • .sh
  • .md
  • .aup
  • .gadget
  • .lvl
  • .text
  • .war
  • .wdgt
  • .pkpass
  • .pl
  • .perl
  • .swf
  • .gzip
  • .mcmeta
  • .wotreplay
  • .mod
  • .wpl
  • .au3
  • .adg
  • .als
  • .alp
  • .ams
  • .amxd
  • .themepack
  • .lua
  • .rsa
  • .img
  • .lnk

It encrypts files found in the following folders:

  • %Desktop%
  • %Application Data%\Microsoft\Windows\Recent
  • %User Profile%\Pictures
  • %User Profile%\Music
  • %User Profile%\Videos
  • %User Profile%\Documents
  • %User Profile%\Downloads
  • %User Profile%\Links
  • %User Profile%\Favorites
  • %User Profile%\Contacts

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It appends the following extension to the file name of the encrypted files:

  • {Original Filename}.{Original File Extension}.Dusk

It drops the following file(s) as ransom note:

  • {Encrypted Directory}\!#!READ-ME!#!.txt

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.412.03
FIRST VSAPI PATTERN DATE: 14 Dec 2020
VSAPI OPR PATTERN File: 16.413.00
VSAPI OPR PATTERN Date: 15 Dec 2020

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Troj.Win32.TRX.XXPE50FFF039

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Profile%\WindowsUpdateTemp.bat
  • {Encrypted Directory}\!#!READ-ME!#!.txt

Step 5

Enabling Volume Shadow Service

  1. Run the command prompt (cmd.exe) as administrator.
  2. Enable Volume Shadow Service by typing the following command:
    net start vss

Step 6

Scan your computer with your Trend Micro product to delete files detected as Ransom.MSIL.DUSK.B. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:

Step 7

Restore encrypted files from backup.


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